http://code.google.com/p/v8/wiki/Source?tm=4
svn checkout http://v8.googlecode.com/svn/trunk/ v8 
svn co http://gyp.googlecode.com/svn/trunk build/gyp
python build\gyp_v8 --generator-output="out" -Dv8_target_arch=ia32
set GYP_GENERATORS=make
mingw32-make -C out -f Makefile BUILDTYPE=Release builddir="f:\temp\v8\out\ia32.release"


cd out
mingw32-make BUILDTYPE=Release


scons os=win32 toolchain=gcc library=shared

Compiled v8 using:
set PATH=C:\Python27;C:\Python27\Scripts;C:\mingw64-4.5.2-tdm64-1\bin;%SystemRoot%\System32
scons mode=debug arch=x64 toolchain=gcc importenv=PATH

Compiled attached hello_world.cpp example using:
g++ -g -I include hello_world.cpp libv8_g.a -lws2_32 -lwinmm

Anyone have any idea why this assert may be failing?